ESTA - Electronic System for Travel Authorization
It is mandatory for anyone travelling to or transferring through the US under the Visa Waiver Program, to obtain approval to travel no later than 72 hours prior to travel by completing an online process ESTA (Electronic System for Travel Authorisation (ESTA) scheme. The cost of an ESTA is currently approx $14 per person and can be obtained by visiting https://esta.cbp.dhs.gov or the Visit USA Website at www.visitusa.org.uk where further information on the scheme and up to date fee can also be found. Once completed & approved, the ESTA application is valid for two years and allows multiple visits without the need to reapply. Travellers can apply for an ESTA even if they have no firm plans to travel to the US.
Failure to obtain an ESTA could result in the passenger being denied boarding by the airline.
The ESTA is very similar to the automated visa that you purchase to enter Australia and is completely paperless.